Organic light-emitting element and light-emitting device with the organic light-emitting element

ABSTRACT

The present invention provides a white organic light-emitting element high in the emission efficiency. In particular, the invention provides a white organic light-emitting element that has an emission spectrum having peaks in the respective wavelength regions of red color, green color and blue color and is high in the emission efficiency. It is preferable to use an electron transport material between a first emission region and a second emission region and more preferable to use a hole block material.

TECHNICAL FIELD

The present invention relates to an organic light-emitting element thatcomprises an anode, a cathode, and a layer containing an organiccompound (hereinafter, electroluminescent layer) that generates light byapplying electric field through the electrodes; and a light-emittingdevice that comprises the organic light-emitting element. Specifically,the present invention relates to a light-emitting element that exhibitswhite emission and a full color light-emitting device comprising theorganic light-emitting element.

BACKGROUND ART

An organic light-emitting element emits light when electric field isapplied thereto. The emission mechanism is a carrier injection type.That is, by applying voltage through a pair of electrodes thatinterposes an electroluminescent layer therebetween, electrons injectedfrom a cathode and holes injected from an anode are recombined withinthe electroluminescent layer to form molecules in excited states(hereinafter, excited molecule), and the excited molecules return to theground state while radiating energy to emit light.

There are two excited states possible from organic compounds, thesinglet state and the triplet states. Light emission from the singletstate is referred to as fluorescence and the same from the triplet stateis referred to as phosphorescence.

In such organic light-emitting element, an electroluminescent layer isgenerally formed to have a thickness of below 1 μm. Further, since theorganic light-emitting element is a self-luminous element in which anelectroluminescent layer emits light, a back light used for theconventional liquid crystal display device is unnecessary. Therefore,the organic light-emitting element has a great advantage of beingmanufactured to have a ultra thin film thickness and light weight.

In the case of an electroluminescent film with a thickness ofapproximately 100 nm to 200 nm, the time between the injection ofcarriers and their recombination is about several ten nanosecondsconsidering the carrier mobility. Hence, the time required for theprocess of injecting carriers and emitting light of theelectroluminescent layer is on the order of microsecond. Thus, anextremely high response speed is one of the advantages thereof.

Further, since an organic light-emitting element is carrier injectiontype, it can be driven by a direct current voltage, thereby noise ishardly generated. With respect to a drive voltage, an electroluminescentlayer is formed into a uniform ultra thin film having a thickness ofapproximately 100 nm, and a material for an electrode is selected toreduce a carrier injection barrier. Further, a hetero structure(two-layers structure) is introduced. Accordingly, a sufficientluminance of 100 cd/m² can be obtained at an applied voltage of 5.5V(non-patent literature 1: C. W. Tang and S. A. VanSlyke, Applied PhysicsLetters, vol. 51, No. 12, pp. 913-915 (1987)).

An organic light-emitting element has been attracted attention as a nextgeneration's device for a flat panel display in terms of the thinthickness and light weight, the high response speed, the direct lowvoltage operation, or the like. In addition, the organic light-emittingelement can be used effectively as the element for the display screen ofa portable electric appliance in terms of the self luminous type, thewide viewing angle, and the high level of visibility.

Wide variations of emission color is also one of the advantages of theorganic light-emitting element. Richness of color is resulted from themultiplicity of an organic compound itself. That is, an organic compoundis flexible enough to be developed to various materials by designingmolecules (such as introducing substituent). Accordingly, the organiclight-emitting element is rich in color.

From these viewpoints, it would not be an overstatement to say that thebiggest application area of an organic light-emitting element is a fullcolor flat panel display device Various means for full colorization havebeen developed in view of characteristics of the organic light-emittingelement. At present, there are three primary methods of forming thestructure of a full color light-emitting device by using the organiclight-emitting element.

First, the method that organic light-emitting elements having threeprimary colors, that is, red (R), green (G), and blue (B) are patterned,respectively, by shadow mask technique to serve them as pixels(hereinafter, RGB method). Second, a blue organic light-emitting elementis used as a light emission source, and the blue emission is convertedinto green or red by color changing material (CCM) made fromphosphorescent material to obtain three primary colors (hereinafter, CCMmethod). Third, a white organic light-emitting element is used as alight emission source, and a color filter (CF) used for a liquid crystaldisplay device or the like is provided to obtain three primary colors(hereinafter, CF method).

Among these, in the CCM system and the CF system, an organiclight-emitting element that is used therein emits monochromatic lightsuch as blue (CCF system) or white (CF system); accordingly, differentfrom the RGB system, precise separate coating by use of a shadow mask isnot necessary. Furthermore, a color conversion material or a colorfilter can be manufactured according to an existing photolithographytechnique, and there is no need of complicated processes. Stillfurthermore, other than merits from a process point of view, there isanother advantage in that since only one kind of element is used, thebrightness varies uniformly with time; accordingly, the color shift orirregular brightness with time are not caused.

However, in case of adopting the CCM method, there has been a problem inred color since color conversion efficiency of from blue to red is poorin principle. In addition, there has been a problem that the contrastbecomes deteriorated since a color conversion material itself isfluorescent so that light is generated in pixels due to outside lightsuch as sunlight. CF method has no such problems since a color filter isused as well as the conventional liquid display device.

Accordingly, although the CF method has comparative few disadvantages,the CF method has a problem that a high efficient white organiclight-emitting element is indispensable to the CF method since a greatdeal of light is absorbed into the color filter. A mainstream whiteorganic light-emitting element is the element that combinescomplementary colors such as blue and yellow) (hereinafter, twowavelengths white light-emitting element) instead of white color havingthe peak intensity in each wavelength of R, G, and B (non-patentliterature 2: Kido et al., “46^(th) Applied Physics Relation UnionLecture Meeting” p1282, 28a-ZD-25 (1999)).

However, considering a light-emitting device combined with a colorfilter, a white organic light-emitting element having an emissionspectrum with the peak intensity in each wavelength of R, G, and B(hereinafter, three wavelengths white light-emitting element) isdesirable instead of the two wavelengths white light-emitting element,which was reported in the non-patent literature 2.

Such three wavelengths white light-emitting element has been reportedseveral times (for instance, non-patent literature 3: J. Kidoatal.,Science, vol. 267, 1332-1334 (1995)). However, such three wavelengthswhite light-emitting element is inferior to the two wavelengths whitelight-emitting element in terms of luminous efficiency, consequently,significant improvement is required.

Furthermore, irrespective of two-wavelength type or three-wavelengthtype, white emission can be applied also to lighting and so on. Fromsuch meaning too, development of a highly efficient white organiclight-emitting element is desired.

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

In this connection, the present invention intends to provide a whileorganic light-emitting element that is high in the emission efficiency.In particular, the invention intends to provide a white organiclight-emitting element that has an emission spectrum that has peaks inthe respective wavelength regions of red color, green color and bluecolor and is high in the efficiency.

Furthermore, the invention intends, by manufacturing a light-emittingdevice with the organic light-emitting element, to provide alight-emitting device that is lower in the power consumption more thanever. In the present specification, “a light-emitting device” indicatesa light-emitting device or an image display device that uses an organiclight-emitting element. Furthermore, all of a module in which to anorganic light-emitting element a connector such as a flexible printedcircuit (FPC) or a TAB (Tape Automated Bonding) tape or a TCP (TapeCarrier Package) is attached, a module in which to a tip end of the TABor TCP a printed wiring board is disposed, or a module in which an IC(integrated circuit) is directly mounted on an organic light-emittingelement according to a COG (Chip On Glass) method are included in thelight-emitting device.

Means for Solving the Problems

In the case of a white emission spectrum, in particular, an emissionspectrum having peaks in the respective wavelength regions of red color,green color and blue color, it is considered that a spectrum regionpoorest in the emission efficiency is a red region. This is because theemission efficiencies of red emitting materials are generally lower thanthat of others. In view of the circumstance, the present inventionintends to realize a highly efficient white organic light-emittingelement by introducing a reddish phosphorescent material.

A phosphorescent material is a material that can convert a tripletexcitation state to emission, that is, a material that can emitphosphorescence. It is known that since in an organic light-emittingelement it is considered that a singlet excitation state and a tripletexcitation state are generated at a ratio of 1:3, when a phosphorescentmaterial is used high emission efficiency can be achieved.

However, in the case of a red phosphorescent material being introducedin a structure of a white organic light-emitting element such as shownin non-patent literature 2, only the red color is emitted, othercomponents such as blue one or green one cannot be observed. As aresult, white emission cannot be obtained. That is, since aphosphorescent material easily converts excitation energy larger thanitself to emission of itself, a white organic light-emitting element inwhich a reddish phosphorescent material is introduced can be said to bedifficult to realize.

The present inventors found, after studying hard, that by applying anelement structure shown below a white organic light-emitting element inwhich a reddish phosphorescent material is introduced can be realized.

That is, a configuration of the present invention is characterized inthat in an organic light-emitting element in which an electroluminescentlayer that has a first emission region and a second emission region themaximum peak of an emission spectrum of which is located in a longerwavelength side than the first emission region is disposed between ananode and a cathode, emission in the second emission region is one froma triplet excitation state and the second emission region is locatedapart from the first emission region.

In the above, the second emission region is preferably constituted of ahost material and a guest material that exhibits emission from a tripletexcitation state.

Furthermore, the configurations are particularly effective when theemission from the first emission region is one from a singlet excitationstate. Accordingly, in the invention, the emission from the firstemission region is characterized by being the emission from a singletexcitation state. In this case, a configuration of the first emissionregion is preferably one that includes a host material and one kind or aplurality of guest materials that exhibits emission from a singletexcitation state.

Still furthermore, a more preferable configuration in the abovementionedorganic light-emitting element according to the invention is one inwhich the first emission region is located toward an anode more than thesecond emission region. In this case, in order to design a carrierrecombination region in the neighborhood of the first emission region,between the first emission region and the second emission region, alayer made of a hole block material that has an ionization potentiallarger than a substance having the largest ionization potential ofsubstances contained in the first emission region is preferablydisposed. A value of the ionization potential of the hole block materialis preferably 0.4 eV or more larger than a value of the ionizationpotential of a substance that has the largest ionization potential ofsubstances contained in the first emission region.

Furthermore, in the configuration according to the invention, in orderto allow both of the first emission region and the second emissionregion to emit efficiently, a distance between the first emission regionand the second emission region is preferably 1 nm or more and 30 nm orless. More preferably, it is 5 nm or more and 20 nm or less.

One of intentions of the invention is to manufacture a highly efficientwhite organic light-emitting element. At this time, when light that isgenerated from the first emission, region on a shorter wavelength sideand light that is generated from the second emission region on a longerwavelength side are combined with a good balance, high quality whiteemission can be realized. Accordingly, an emission wavelength of thefirst emission region and that of the second emission region preferablysatisfy the conditions below.

That is, in the invention, an emission spectrum in the first emissionregion has at least one peak in a region of 400 nm or more and 500 nm orless. Alternatively, it has at least two peaks in a region of 400 nm ormore and 560 nm or less.

Furthermore, an emission spectrum in the second emission region has atleast one peak in a region of 560 nm or more and 700 nm or less.

When the first and second emission regions that exhibit emission in thewavelength regions as mentioned above are combined, highly efficient andhigh-quality white organic light-emitting element can be obtained.

Here, as the emission in the first emission region, excimer emission canbe used. When thus configured, since emission having two peaks can beeasily taken out of the first emission region, when this is combinedwith the emission from the second emission region, white emission havingpeaks in the respective wavelength regions of R, G and B can be easilyrealized. Accordingly, in the invention, in the case of an emissionspectrum in the first emission region having at least two peaks in aregion of 400 nm or more and 560 nm or less, the emission in the firstemission region includes excimer emission.

In the abovementioned organic light-emitting element according to theinvention, the emission in the second emission region is one from atriplet excitation state. As materials that exhibit such an emission, anorganometallic complex can be preferably used. Furthermore, inparticular, from the highness of the emission efficiency, theorganometallic complex that has iridium or platinum as a central metalcan be preferably used.

When a light-emitting device is prepared by use of the abovementionedorganic light-emitting element according to the invention, alight-emitting device having lower power consumption more than ever canbe provided. Accordingly, the invention includes a light-emitting devicethat uses an organic light-emitting element according to the inventionas well.

Advantages of the Invention

By practicing the present invention, a white organic light-emittingelement having high light emission efficiency can be provided.Especially, a high efficient white organic light-emitting element, whichhas the peak intensity in each wavelength region of red, green, andblue, can be provided. Moreover, by manufacturing a light-emittingdevice using the organic light-emitting element, a light-emittingdevice, which operates at lower power consumption than that of theconventional light-emitting device, can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a basic structure of an organiclight-emitting element according to the present invention.

FIGS. 2A and 2B are diagrams showing an emission mechanism in theorganic light-emitting element according to the invention.

FIG. 3 is a diagram showing a specific element structure of the organiclight-emitting element according to the invention (examples 1 through3).

FIGS. 4A through 4C are diagrams showing emission spectra of organiclight-emitting elements in examples 1 through 3.

FIGS. 5A and 5B are schematic diagrams of the light-emitting deviceaccording to the invention (example 4).

FIGS. 6A and 6B are schematic diagrams of the light-emitting deviceaccording to the invention (examples 5 and 6).

FIGS. 7A through 7G are diagrams showing examples of electric appliancesthat use the light-emitting device according to the invention (example7).

FIGS. 8A through 8C are diagrams showing an example of an electricappliance that uses the light-emitting device according to the invention(example 7).

FIG. 9 is a diagram showing a basic structure of an existing organiclight-emitting element.

FIGS. 10A and 10B are diagrams showing an emission mechanism in theexisting organic light-emitting element.

FIG. 11 is a diagram showing a specific element structure of theexisting organic light-emitting element (comparative example 1).

FIG. 12 is a diagram showing an emission spectrum of the organiclight-emitting element in comparative example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below.

Embodiment 1

In what follows, of embodiments of the invention, principles ofoperation and specific examples of configuration are cited and detailed.In an organic light-emitting element, in order to extract emission, anyone of electrodes has only to be transparent. Accordingly, not only anexisting element structure in which a transparent electrode is formed ona substrate and light is extracted from a substrate side but also astructure in which light is actually extracted from a side opposite tothe substrate and a structure in which light is extracted from bothsides of an electrode can be applied.

Firstly, of an existing white organic light-emitting element that hastwo emission regions, that is, a first emission region and a secondemission region a maximum peak of an emission spectrum of which islocated in a longer wavelength side than the first emission region, anexample of a basic configuration thereof is shown in FIG. 9.

FIG. 9 shows a structure of an organic light-emitting element in which alaminated structure (electroluminescent layer 903) of a hole transportlayer 911 made of a hole transport material 921 and an electrontransport layer 912 made of an electron-transporting material 922 issandwiched between an anode 901 and a cathode 902. However, a firstemission region 913 where a first dopant 923 is added to the holetransport layer 911 and a second emission region 919 where a seconddopant 924 is added to the electron transport layer 912 are disposed.That is, the hole transport material 921 and the electron transportmaterial 922 each work as a host material. Furthermore, both of thefirst emission region 913 and the second emission region 914 are presentin the neighborhood of an interface 915 between the hole transport layer911 and the electron transport layer 912.

In such a structure, a recombination region of carriers is in theneighborhood of the interface 915. Since in the neighborhood of theinterface 915 two kinds of the first dopant 923 and the second dopant924 are present together, emission processes are competed between thetwo kinds of dopants. At this time, when the two kinds of dopants areboth fluorescent materials, since excitation lifetimes there of are bothsimilarly short, unless a Förster type energy transfer condition (anemission wavelength of any one of dopants overlaps with an absorptionwavelength of another dopant) is sufficiently satisfied, both two kindscan emit. As a result, white emission can be realized.

For instance, though a structure of a white organic light-emittingelement shown in non-patent literature 2 is one that is obtained byfurther adding another electron transport layer and electron injectionlayer in FIG. 9, a basic principle is similar. That is, in the holetransport layer 911 perylene that is a blue-emitting material isintroduced as the first dopant 923 and in the electron transport layer912 DCM1 that is an orange-emitting material is introduced as the seconddopant 924, and thereby white emission is obtained.

On the other hand, the gist of the invention is to aim higher efficiencyby introducing a reddish phosphorescent material in a white organiclight-emitting element. However, even when a reddish phosphorescentmaterial is introduced in the structure shown in FIG. 9 as the seconddopant 924, white emission cannot be obtained. For instance, even whenan element in which perylene that is a blue-emitting material is used asthe first dopant 923 and as the second dopant 924 2, 3, 7, 8, 12, 13,17, 18-octaethyl-21H, 23H-porphyrin-platinum complex (herein afterabbreviated as PtOEP) that is a red phosphorescent material is used isprepared, only red emission of PtOEP is observed (described later incomparative example 1). This is explained as follows.

Firstly, in order to obtain white emission in the element structure, atleast perylene that is the first dopant 923 has to emit. That is, aminimum condition is that a singlet excitation state of perylene emitslight as it is.

However, as shown in FIG. 10A, without restricting to PtOEP, since manyof phosphorescent materials are small in the ionization potential (aposition of a HOMO level 1001 is high), it forms a deeper trap level toa hole. Accordingly, PtOEP traps a hole, and without exciting perylene,the PtOEP is likely to be directly excited.

Furthermore, many of the phosphorescent materials typical in PtOEP havea broad absorption band called a triplet MLCT in a visible light region(this corresponds to a lowest triplet excitation state of aphosphorescent material). In addition to this, in the case of theFörster type energy transfer, an energy transfer from a singletexcitation state of one molecule to a triplet excitation state ofanother molecule is allowed. This means that, as shown in FIG. 10B, evenwhen a substance (perylene here) that has emission in a visible lightregion is excited, from the singlet excitation state S_(D1) thereof to atriplet excitation state T_(D2) of the phosphorescent material (PtOEPhere), a Förster type energy transfer 1011 can easily occur.Accordingly, emission of perylene becomes difficult to observe. Here,though a triplet excitation state of perylene is not considered here,since perylene is a fluorescent material, the triplet excitation statethere of is deactivated or transfers energy to PtOEP.

Still furthermore, since the triplet MLCT absorption is generally widein the band width, an energy transfer not only from a blue-emittingsubstance such as perylene but also even from a substance exhibitinggreenish emission is induced. This phenomenon occurs not only in thecase where a fluorescent material such as perylene is used as anemitting material in the first emission region but also similarly in thecase where a phosphorescent material is used. Accordingly, a whiteorganic light-emitting element in which a reddish phosphorescentmaterial is introduced can be realized with difficulty.

A method of overcoming the problem is to make a distance between a firstemission region and a second emission region more distant and thereby toinhibit an excitation state of the first emission region (singletexcitation state in particular) from being transferred to a tripletexcitation state of the second emission region. An example of such abasic configuration of the invention is shown in FIG. 1.

In FIG. 1, a first dopant (fluorescent material here) 123 is added to ahole transport layer 111 that is made of a hole transport material 121and thereby a first emission region 113 is formed. Furthermore, a seconddopant (phosphorescent material) 129 is added to an electron transportlayer 112 that is made of an electron transport material 122 and therebya second emission region 114 is formed. As to emission wavelength, oneof the second dopant (phosphorescent material) 124 is located toward alonger wavelength side than one of the first dopant 123. Furthermore,between the first emission region 113 and the second emission region114, a layer 116 (hereinafter referred to as “gap layer”) to which thesecond dopant (phosphorescent material) 124 is not added is disposedwith a thickness of d, and this point is different from FIG. 9. Here thegap layer 116 is assumed to have the electron transportability. Stillfurthermore, reference numerals 101, 102 and 103, respectively, denotean anode, a cathode and an electroluminescent layer.

At this time, since the gap layer 116 has the electron transportability,at recombination region in the structure is in the neighborhood of aninterface 115 between the first emission region 113 and the gap layer116. Furthermore, as shown in FIG. 2A, owing to a distance d, a HOMOlevel 201 of the second dopant (phosphorescent material) does notdirectly trap a hole. Accordingly, firstly, the first dopant 123 isexcited. As an excitation state, there are a singlet excitation stateS_(D1) and a triplet excitation state T_(D1).

Here, as shown in FIG. 2B, since owing to the gap layer 116 the firstdopant and the second dopant (phosphorescent material) are apart by adistance d, the aforementioned Förster type energy transfer 211 ofS_(D1)→T_(D2)contributes less (drastically diminishes as the distance dbecomes larger). By just that much, S_(D1)→G_(D1) that is, emission ofthe first dopant hv_(D1) becomes to be observed.

On the other hand, since the first dopant is a fluorescent materialhere, the triplet excitation state T_(D1) cannot emit but can transferenergy to a triplet excitation state T_(D2) of the second dopant(phosphorescent material). An excitation lifetime of a tripletexcitation molecule is normally longer than that of a singlet excitationmolecule and a diffusion distance thereof is large; accordingly, incomparison with the aforementioned energy transfer 211 of S_(D1)→T_(D2),an energy transfer 212 of T_(D1)→T_(D2) is affected less by a distanced. Accordingly, even when a distance d is separated to some extent, theenergy transfer of T_(D1)→T_(D2) is effectively caused, subsequently, atriplet excitation state T_(D2) of the second dopant (phosphorescentmaterial) is speedily converted into emission hv_(D2).

As described above, when the element structure according to theinvention is applied, both the first dopant and the second dopant(phosphorescent material) that exhibits an emission in a longerwavelength side than the first dopant are allowed to emit; accordingly,white emission can be attained.

In the element structure shown in FIG. 1, in the second emission region,a phosphorescent material is used as a dopant; however, a phosphorescentmaterial can be used singularly.

Furthermore, as a luminescent material in the first emission region, aphosphorescent material may be used; however, as shown in FIG. 1, afluorescent material can be used preferably. In this case, a generatedsinglet excitation state and a generated triplet excitation state,respectively, contribute to emissions mainly in the first emissionregion and the second emission region; accordingly, both excitationstates of the singlet and the triplet are allowed to contribute toemission and thereby an increase in the efficiency can be expected.Furthermore, an emission mechanism is understandable and an element canbe easily designed.

Still furthermore, in the first emission region of the invention,without using a dopant, a layer that emits singularly may be applied.However, since the use of the dopant generally makes the emissionefficiency higher, the dopant is preferably used as shown in FIG. 1.Furthermore, as mentioned above, since as a luminescent material in thefirst emission region a fluorescent material is preferable, it is thebest to use a fluorescent material as the dopant in the first emissionregion. In that case, a plurality of kinds of dopants may be used.

The element configuration shown in FIG. 1 is one example of theinvention and the element configuration, as far as it does not deviatefrom the gist of the invention, is not restricted thereto. For instance,in FIG. 1, a configuration in which in the hole transport layer 111 thesecond dopant (phosphorescent material) is doped, and in the electrontransport layer 112 the first dopant is doped (that is, in this case,the second emission region becomes 113 and the first emission regionbecomes 114) may be formed. In this case, the gap layer 116 isnecessarily constituted of a hole-transporting material and arecombination region of carriers is necessarily designed at an interfacebetween the gap layer 116 and the electron transport layer 112.

Furthermore, though not shown in FIG. 1, between the anode 101 and thehole transport layer 111, a hole injection layer or a hole transportlayer made of a hole transport material other than the hole transportmaterial 121 may be inserted. Still furthermore, between the cathode 102and the electron transport layer 112, an electron injection layer or anelectron transport layer made of an electron transport material otherthan the electron transport material 122 may be inserted.

As mentioned above, the invention pays attention to a point that firstlyan excitation state is formed in the first emission region and energythereof is partially transferred to the second emission region. Fromsuch a viewpoint, like the structure shown in FIG. 1, the first emissionregion 113 is preferably designed more toward the anode than the secondemission region 114. This is because when at this time a hole blocklayer made of a hole block material is applied as the gap layer 116,holes can be more effectively confined within the hole transport layer111; accordingly, the recombination region of the carriers can bedecided to the first emission region 113.

A value of ionization potential of the hole block material is preferablylarger by 0.4 eV or more than a value of ionization potential of asubstance that has the largest ionization potential of substancescontained in the first emission region 113. Furthermore, when as shownin FIG. 1 the first emission region 113 has a dopant, it is importantthat substantially a value of the ionization potential of the hole blockmaterial that is used in the gap layer 116 is larger (preferably largerby 0.4 eV or more) than a value of the ionization potential of the holetransport material 121 that is a host in the first emission region.

When an element is designed thus, it becomes easy to form an excitationstate in the first emission region firstly and to partially transferenergy thereof to the second emission region. However, in the next, adistance d that governs the energy transfer thereof is necessary to bedecided.

Firstly, when d is set at 1 nm or more, since a Dexter type energytransfer (energy transfer due to exchange of the wave motion of anelectron) can be inhibited from occurring and thereby an energy transfermechanism becomes solely due to the Förster type energy transfer, theabovementioned principle can be applied. Furthermore, when d is set atsubstantially 30 nm, even the energy transfer due to T_(D1)→T_(D2)described in FIG. 2B tends to decrease much. Accordingly, the d ispreferably in the range of 1 nm or more and 30 nm or less.

However, in order to inhibit the phosphorescent material in the secondemission region from directly trapping the holes (FIG. 2A), the d ispreferably set at 5 nm or more. Furthermore, a proper distance thatmakes the contribution of the energy transfer 211 of S_(D1)→T_(D2)inFIG. 2B smaller and further sufficiently causes the energy transfer 212of T_(D1)→T_(D2) is substantially 5 to 20 nm. Accordingly, the d is morepreferably 5 nm or more and 20 nm or less.

In the above, a principle that according to the present invention awhite organic light-emitting element in which a reddish phosphorescentmaterial is introduced can be realized was described. In the next place,a wavelength range preferable for obtaining a high-quality whiteemission color will be illustrated.

Firstly, an emission spectrum in the first emission region has at leastone peak in a region of 900 nm or more and 500 nm or less or at leasttwo peaks in a region of 400 nm or more and 560 nm or less. When this iscombined with an emission color of a reddish phosphorescent material inthe second emission region, white light can be realized. At this time,an emission spectrum of the phosphorescent material has only to bereddish, that is, to have at least one peak in a region of 560 nm ormore and 700 nm or less.

Furthermore, when for instance a first dopant that is capable ofexhibiting the excimer emission is added to the first emission region,by optimizing a doping concentration, emission intrinsic to the firstdopant and excimer emission thereof are allowed to simultaneously emit.Since the excimer emission is necessarily located on a longer wavelengthside than the intrinsic emission, two emission peaks can be extractedfrom one substance. When this phenomenon and a reddish Emission color inthe second emission region are combined, an emission spectrum havingpeaks in the respective wavelength regions of R, G and B can berealized.

In what follows, materials that can be used in the invention will bespecifically illustrated. However, materials that can be applied to theinvention are not restricted thereto.

As a hole injection material that is used in a hole injection layer,porphyrin base compounds are effective among organic compounds; that is,phthalocyanine (abbreviated as H₂-Pc), copper phthalocyanine(abbreviated as Cu-Pc) and so on can be used. Furthermore, there arematerials obtained by applying the chemical doping to conductivepolymers; that is, polyethylene dioxythiophene (abbreviated as PEDOT),polyaniline (abbreviated as PAni) and polyvinyl carbazole (abbreviatedasPVK) that are doped with polystyrene sulfonic acid (abbreviated asPSS) can be used. Still furthermore, very thin films of inorganicinsulators such as vanadium pentoxide and aluminum oxide are effectiveas well.

As a hole transport material for using a hole transporting layer,aromatic amine (that is, the one having a benzene ring-nitrogen bond)compounds are preferably used. For example, N, N′-bis(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine(abbreviated TPD) or derivativesthereof such as 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl(hereafter, referred to as α-NPD) is widely used. Also used are starburst aromatic amine compounds, including:4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine(hereafter, referred toas TDATA); and 4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine (hereafter, referred to as “MTDATA”).

As electron transport materials for forming an electron transportinglayer, in specific, metal complexes such tris(8-quinolinolate) aluminum(abbreviated Alq₃), tris(4-methyl-8-quinolinolate)aluminum(abbreviatedAlmq₃), bis(10-hydroxybenzo[h]-quinolinato) beryllium (abbreviatedBeBq₂), bis(2-methyl-8-quinolinolate)-(4-hydroxy-biphenylyl)-alum inum(abbreviated BAlq), bis [2-(2-hydroxyphenyl)-benzooxazolate] zinc(abbreviated Zn(BOX)₂), and bis[2-(2-hydroxyphenyl)-benzothiazolate]zinc (abbreviated Zn(BTZ)₂). Besides, oxadiazole derivatives such as2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviatedPBD), and 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl] benzene(abbreviated OXD-7); triazole derivatives such as3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-tr iazole(abbreviated TAZ) and3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviated p-EtTAZ); imidazol derivatives such as2,2′,2″-(1,3,5-benzenetryil)tris[1-phenyl-1H-benzimidazol e](abbreviated TPBI); and phenanthroline derivatives such asbathophenanthroline (abbreviated BPhen) and bathocuproin (abbreviatedBCP) can be used in addition to metal complexes.

Furthermore, as hole block materials that are useful as the materialsfor the abovementioned gap layer, abovementioned BAlq, OXD-7, TAZ,p-EtTAZ, TPBI, BPhen and BCP can be used.

Still furthermore, as the luminescent materials in the first emissionregion, fluorescent materials having the hole transportability such asabovementioned TPD and α-NPD and fluorescent materials having theelectron transportability such as Alq₃, Almq₃, BeBq₂, BAlq, Zn(BOX)₂ andZn(BTZ)₂ may be used. Furthermore, various kinds of fluorescent dyessuch as quinacridone, N, N′-dimethyl quinacridone, perylene,fluoranthene, and cumarine base dyes (such as cumarone 6) can be citedas dopant. Still furthermore, phosphorescent materials such as tris(2-phenylpyridine) iridium (abbreviated as Ir(ppy)₃) can be cited. Allthese exhibit an emission peak in 400 nm or more and 560 nm or less;accordingly, these can be preferably used as a luminescent material inthe first emission region.

On the other hand, as a luminescent material in the second emissionregion, an organometallic complex having iridium or platinum as acentral metal is effective. Specifically, other than the abovementionedPtOEP, bis (2-(2′-benzothienyl) pyridinato-N, C³′)(acetylacetonato)iridium (abbreviated as btp₂Ir(acac)),bis(2-(2′-thienyl) pyridinato-N, C³′ (acetylacetonato) iridium(abbreviated as thp₂Ir(acac)) and bis(2-(1-naphthyl)benzooxazolato₇N,C²′(acetylacetonato)iridium(abbreviated as bon₂Ir (acac)) can be cited.All these are phosphorescent materials having a reddish (560 nm or moreand 700 nm or less) emission peak and suitable as a luminescent materialin the second emission region according tot the invention.

In the case of a dopant being used in the first emission region or thesecond emission region, as a host material thereof, a hole transportmaterial or an electron transport material typical in the abovementionedexamples can be used. Furthermore, a bipolar material such as 4, 4′-N,N′-dicarbazolyl-biphenyl (abbreviated as CBP) can be used.

Furthermore, in the invention, a lamination method of the respectivelayers in an organic light-emitting element is not restricted toparticular one. As far as the lamination can be carried out, whatevermethod of vacuum deposition method, spin coat method, ink jet method anddip coat method can be selected.

EXAMPLES Example 1

In the present example, an organic light-emitting element according tothe invention and having a gap layer thickness d of 10 nm will bespecifically illustrated with reference to FIG. 3. In FIG. 3, referencenumerals 301, 302 and 303, respectively, denote an anode, a cathode andan electroluminescent layer.

Firstly, on a glass substrate on which ITO that is an anode 301 wasdeposited with a thickness of substantially 100 nm, CuPc that is a holetransport material was deposited with a thickness of 20 nm, and therebya hole injection layer 310 was formed. Subsequently, α-NPD that is ahole transport material was deposited with a thickness of 30 nm, andthereby a hole transport layer 311 was formed. In the last 10 nmthereof, α-NPD (host material) and perylene (guest material) that is asinglet emission material were co-deposited so as to be substantially99:1 in the ratio thereof (weight ratio). That is, at a concentration ofsubstantially 1 weight percent, perylene is dispersed in α-NPD. Thisco-deposited layer of 10 nm is a first emission region 313.

After the first emission region 313 was formed, BAlq that is a holeblock material (and an electron transport material) was deposited with athickness of 10 nm, and thereby a gap layer 316 was formed. BAlq wasfurther deposited with a thickness of 30 nm as an electron transportlayer 312. In the first 10 nm thereof, a region to which aphosphorescent material PtOEP was added was co-deposited to form. Anaddition amount was controlled so that in BAlqPtOEP may be dispersed ata concentration of substantially 7.5 weight percent. This becomes asecond emission region 314. Thus, a layer that uses BAlq becomes in sumtotal 40 nm in a combination of the gap layer 316 and the electrontransport layer 312.

In the next place, Alq that is an electron transport material wasdeposited with a thickness of 20 nm and thereby a second electrontransport layer 317 was formed. Thereafter, as an electron injectionlayer 318, 2 nm of calcium fluoride (abbreviated as CaF₂) was deposited,finally followed by depositing 150 nm of Al as a cathode. Thereby, anorganic light-emitting element according to the invention can beobtained.

The characteristics of the organic light-emitting element manufacturedaccording to example 1 were as follows. That is, when the brightness wasset at 10 [cd/m²], a driving voltage was 8.0 [V] and a currentefficiency was 4.7 [cd/A].

An emission spectrum when the brightness is 10 [cd/m²] is shown in FIG.4A. A blue emission spectrum 901 intrinsic to perylene and a greenspectrum 402 due to the excimer emission of perylene, respectively, wereclearly observed in the neighborhood of 460 nm and 980 nm and in theneighborhood of 520 nm. Furthermore, in the neighborhood of 650 nm, asharp red peak 403 due to PtOEP was observed.

Thus, in the example 1, an organic light-emitting element that uses areddish phosphorescent material and has peaks in the respectivewavelength regions of R, G and B could be realized. The CIE colorcoordinates were (x, y)=(0.30, 0.35), and it was white emission to theeye.

As mentioned above, it is considered that in the example 1, the energytransfer of S_(D1)!T_(D2) shown in FIG. 2B is suppressed to some extentand thereby both perylene and PtOEP are allowed to emit.

Ionization potentials of α-NPD that was used in the hole transport layer311 and BAlq that was used in the gap layer 316 were measured (in a thinfilm state by use of a photoelectron spectrometer AC-2 manufactured byRiken Keiki Co., Ltd.) and found to be 5.3 [eV] for α-NPD and 5.7 [eV]for BAlq. That is, it is considered that owing to difference ofsubstantially 0.9 [eV] in the ionization potentials of both, BAlqeffectively blocks holes and controls the recombination region ofcarriers within the hole transport layer 311 (or in the first emissionregion 313).

Example 2

In the present example, an organic light-emitting element according tothe invention and having a gap layer thickness d of 20 nm will bespecifically illustrated with reference to FIG. 3.

Firstly, the first emission region 313 is formed similarly to example 1.After the first emission region 313 is formed, BAlq that is a hole blockmaterial (and an electron transport material) was deposited with athickness of 20 nm and thereby a gap layer 316 was formed. BAlq wasfurther deposited with a thickness of 20 nm as an electron transportlayer 312. In the first 10 nm thereof, a region to which aphosphorescent material PtOEP was added was co-deposited to form. Anaddition amount was controlled so that in BAlq PtOEP may be dispersed ata concentration of substantially 7.5 weight percent. This becomes asecond emission region 314. Thus, a layer that uses BAlq becomes in sumtotal 40 nm in combination of the gap layer 316 and the electrontransport layer 312.

In the next place, Alq that is an electron transport material wasdeposited with a thickness of 20 nm, and thereby a second electrontransport layer 317 was formed. Thereafter, as an electron injectionlayer 318, 2 nm of CaF₂ was deposited, finally followed by depositing150 nm of Al as a cathode. Thereby, an organic light-emitting elementaccording to the invention can be obtained.

The characteristics of the organic light-emitting element manufacturedaccording to example 2 were as follows. That is, when the brightness wasset at 10 [cd/m²], a driving voltage was 8.6 [V] and a currentefficiency was 4.6 [cd/A].

An emission spectrum when the brightness is set at 10 [cd/m²] is shownin FIG. 9B. A blue emission spectrum 401 intrinsic to perylene and agreen spectrum 402 due to excimer emission of perylene, respectively,were clearly observed in the neighborhood of 460 nm and 480 nm and inthe neighborhood of 520 nm. Furthermore, in the neighborhood of 650 nm,a sharp red peak 403 due to PtOEP was observed.

Thus, also in the example 2, an organic light-emitting element that usesa reddish phosphorescent material and has peaks in the respectivewavelength regions of R, G and B could be realized. The CIE colorcoordinates were (x, y)=(0.25, 0.36), and it was bluish white emissionto the eye.

As mentioned above, it is considered that in the example 2, the energytransfer of S_(D1)→T_(D2)shown in FIG. 2B is substantially completelysuppressed and thereby both perylene and PtOEP were allowed to emit.

Example 3

In the present-example, an organic light-emitting element according tothe invention and having a gap layer thickness d of 30 nm will bespecifically illustrated with reference to FIG. 3.

Firstly, the first emission region 313 is formed similarly to examples 1and 2. After the first emission region 313 was formed, BAlq that is ahole block material (and an electron transport material) was depositedwith a thickness of 30 nm, and thereby a gap layer 316 was formed.Furthermore, as a second emission region 314, a region where aphosphorescent material PtOEP was added to BAlq was co-deposited with athickness of 10 nm. An addition amount was controlled so that in BAlqPtOEP may be dispersed at a concentration of substantially 7.5 weightpercent. Thus, a layer that uses BAlq becomes in sum total 90 nm incombination of the gap layer 316 and the second emission region 319. Inthe example, after the second emission region 314, BAlq is not furtherformed as an electron transport layer 312 (this is because a filmthickness of layers that use BAlq is made 40 nm similarly to examples 1and 2).

In the next place, Alq that is an electron transport material wasdeposited with a thickness of 20 nm and thereby a second electrontransport layer 317 was formed. Thereafter, as an electron injectionlayer 318, 2 nm of CaF₂ was deposited, finally followed by depositing150 nm of Al as a cathode. Thereby, an organic light-emitting elementaccording to the invention can be obtained.

The characteristics of the organic light-emitting element manufacturedaccording to example 3 were as follows. That is, when the brightness wasset at 10 [cd/m²], a driving voltage was 8.2 [V] and a currentefficiency was 4.6 [cd/A].

An emission spectrum when the brightness is set at 10 [cd/m²] is shownin FIG. 4C. A blue emission spectrum 401 intrinsic to perylene and agreen spectrum 902 due to excimer emission of perylene, respectively,were clearly observed in the neighborhood of 460 nm and 480 nm and inthe neighborhood of 520 nm. Furthermore, in the neighborhood of 650 nm,though a little weak, a sharp red peak 403 due to PtOEP was alsoobserved.

Thus, also in the example 3, an organic light-emitting element that usesa red phosphorescent material and has peaks in the respective wavelengthregions of R, G and B could be realized. The CIE color coordinates were(x, y)=(0.22, 0.35), and it was bluish blue-white to the eye.

As mentioned above, it is considered that in the example 3, the energytransfer of S_(D1)→T_(D2)shown in FIG. 2B was substantially completelysuppressed and furthermore, in comparison with examples 1 and 2, theenergy transfer due to T_(D1)→T_(D2) was also attenuated; as a result,emission of perylene became stronger, and emission of PtOEP becameweaker. Accordingly, the thickness d of the gap layer according to theinvention can be said to be preferable up to substantially 30 nm.

Comparative Example 1

In the present comparative example, an existing organic light-emittingelement in which a gap layer is not disposed will be specificallyillustrated with reference to FIG. 11. In FIG. 11, reference numeralsand so on in FIG. 3 are quoted.

Firstly, s first emission region 313 is formed similarly to examples 1through 3. After the first emission region 313 was formed, as anelectron transport layer 312 BAlq was deposited with a thickness of 90nm. In the first 10 nm thereof, a second emission region 314 to which aphosphorescent material PtOEP is added with BAlq as a host was formed.An addition amount was controlled so that PtOEP may be dispersed in BAlqat a concentration of substantially 7.5 weight percent.

Subsequently, an electron transport material Alq was deposited with athickness of 20 nm and thereby a second electron transport layer 317 wasformed. Thereafter, as an electron injection layer 317, 2 nm of CaF₂ wasdeposited, followed by finally depositing Al with a thickness of 150 nmas a cathode.

The characteristics of the organic light-emitting element manufacturedaccording to the comparative example were as follows. That is, when thebrightness was set at 10 [cd/m²], a driving voltage was 8.8 [V] and acurrent efficiency was 1.9 [cd/A].

An emission spectrum when the brightness is set at 10 [cd/m²] is shownin FIG. 12. In the comparative example, an emission spectrum of perylenewas hardly observed and only a sharp red peak 1201 due to PtOEP in theneighborhood of 650 nm was observed. Furthermore, the CIE colorcoordinates were (x, y)=(0.51, 0.33), and it was nearly red to the eye.

As shown with the above comparative example, it is found that accordingto the existing element structure in which a gap layer according to theinvention is not disposed, a white organic light-emitting element towhich a reddish phosphorescent material is applied is difficult torealize.

Example 4

In the present example, a light-emitting device that has an organiclight-emitting element according to the invention in a pixel portionwill be explained with reference to FIGS. 5A and 5B. FIG. 5A is a topview showing a light-emitting device and FIG. 5B is a sectional viewobtained by cutting FIG. 5A along A-A′. Reference numerals 501, 502 and503, respectively, denote a driving circuit portion (source side drivingcircuit), a pixel portion and a driving circuit portion (gate sidedriving circuit). Furthermore, reference numerals 504 and 505,respectively, denote a sealing substrate and a sealing agent, and theinside 507 surrounded by the sealing agent 505 is a space.

Reference numeral 508 denotes a connection wiring for transmitting asignal that is input to the source side driving circuit 501 and the gateside driving circuit 503 and the connection wiring 508 receives from anFPC (flexible printed circuits) 509 that becomes an external inputterminal a video signal, a clock signal, a start signal and a resetsignal. In the drawing, only an FPC is shown; however, to the FPC aprinted wiring board (PWB) may be attached. In the light-emitting devicein the present specification, not only the light-emitting device bodybut also a state where an FPC or PWB is attached thereto is included.

In the next place, a sectional structure will be explained withreference to FIG. 5B. On a substrate 510, a driving circuit portion anda pixel portion are formed. In the drawing, the source side drivingcircuit 501 that is a driving circuit portion and the pixel portion 502are shown.

In the source side driving circuit 501, a CMOS circuit in which ann-channel type TFT 523 and a p-channel type TFT 524 are combined isformed. Furthermore, a TFT that forms a driving circuit may be formedwith a known CMOS circuit, PMOS circuit or NMOS circuit. Furthermore, inthe present embodiment, a driver-integrated type in which a drivingcircuit is formed on a substrate is shown; however, the driving circuitis not necessarily formed on a substrate but may be formed outsidethereof.

Furthermore, the pixel portion 502 is formed of a plurality of pixelsincluding a switching TFT 511, a current control TFT 512 and a firstelectrode 513 electrically connected to a drain thereof. An insulator514 is formed covering an end portion of the first electrode 513. Here,a positive photosensitive acrylic resin film is used to form.

In order to improve the coverage, a curved surface having a curvature isformed at an upper end or lower end of the insulator 519. For instance,in the case of a positive photosensitive acryl being used as a materialof the insulator 514, it is preferable to give a curved surface having aradius of curvature (0.2 to 3 μm) only to the upper end portion of theinsulator 519. As the insulator 514, any one of a negative type thatbecomes insoluble to an etchant owing to photosensitive light and apositive type that becomes soluble to an etchant owing to light can beused.

On the first electrode 513, an electroluminescent layer 515 and a secondelectrode 516 are formed. As a material that is used for the firstelectrode 513 that works as an anode, it is preferable to use a materiallarge in the work function. For instance, other than single layer filmssuch as an ITO (indium tin oxide) film, indium zinc oxide (IZO) film,titanium nitride film, chromium film, tungsten film, Zn film and Ptfilm, a laminate of titanium nitride and a film mainly made of aluminumand a three-layered structure of a titanium nitride film, a film mainlymade of aluminum and a titanium nitride film can be used. When alaminate structure is taken, the laminate is low in the resistance as awiring, can establish good ohmic contact, and is allowed to function asan anode. Here, as the first electrode 513, ITO is used, and a structurewhere light is taken out of a substrate 510 side is adopted.

The electroluminescent layer 515 is formed by means of a vapordeposition method with a deposition mask or an ink jet method. To theelectroluminescent layer 515, an electroluminescent layer having astructure disclosed in the invention has only to be applied.Specifically, configurations of the electroluminescent layer shown inexamples 1 through 3 can be used. Furthermore, as materials that areused in the electroluminescent layer, normally, in many cases, organiccompounds are used in a single layer or laminated layer; however, in theinvention, a configuration in which in a film made of an organiccompound an inorganic compound is partially used is also included.

Furthermore, as materials that are used for the second electrode(cathode) 516 that is formed on the electro luminescent layer 515,materials small in the work function (such as Al, Ag, Li, Ca or alloysthereof such as MgAg, MgIn, AlLi, CaF₂ or CaN) have only to be used. Inthe case of light generated in the electroluminescent layer 515 beingallowed transmitting through the second electrode 516, as the secondelectrode (cathode) 516, a laminate of a metal thin film of which filmthickness is made thin and a transparent conductive film (such as ITO,IZO, and zinc oxide (ZnO)) may be used. Here, by use of anon-transmissive film of Al, a light-emitting device having a bottomemission type structure in which light is extracted only from thesubstrate 510 side is formed.

With the sealing agent 505, a sealing substrate 509 and an elementsubstrate 510 are adhered, and thereby in a space 507 surrounded by thesubstrate 501, the sealing substrate 509 and the sealing agent 505, theorganic light-emitting element 517 according to the invention is housed.In the space 507, other than a case where an inert gas (such as nitrogenor argon) is filled, a configuration that is filled with the sealingagent 505 is also included.

As the sealing agent 505, epoxy base resins can be preferably used.Furthermore, these materials are preferable to be ones that are notpermeable to moisture and oxygen as far as possible. As materials thatare used for the sealing substrate 509, other than a glass substrate orquartz substrate, a plastics substrate made of such as an FRP(Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), mylar,polyester or acryl can be used.

Thus, a light-emitting device having the organic light-emitting elementaccording to the invention can be obtained.

Example 5

In the present example, in a light-emitting device shown in FIG. 5, alight-emitting device having a top emission type structure in whichlight is extracted from the sealing substrate 504 side will bespecifically illustrated. A schematic diagram thereof (sectional view)is shown in FIG. 6A. In FIG. 6A, reference numerals of FIG. 5 arequoted. A direction of emission is shown with 621 in FIG. 6A.

In FIG. 6A, the first electrode 513 and the second electrode,respectively, are made a light-shielding a node and a translucentcathode, and thereby a top emission structure is formed. Accordingly, asthe first electrode, other than single layer films such as a titaniumnitride film, chromium film, tungsten film, an film and Pt film, alaminate of titanium nitride and a film mainly made of aluminum, and athree-layered structure of a titanium nitride film, a film mainly madeof aluminum and a titanium nitride film can be used. As the secondelectrode, a laminate structure of a metal thin film of which filmthickness is made thin and a transparent conductive film (such as ITO,IZO and ZnO) has curly to be used. Here, as the first electrode and thesecond electrode, a titanium nitride film and a laminate structure of athin film of Mg: Ag alloy and ITO are used respectively.

Furthermore, in the light-emitting device according to the example, inorder to make the light-emitting device a full color device with thewhite organic light-emitting element 517 according to the invention, acolor filter (for sake of simplicity, here, an overcoat layer is notshown in the drawing) made of a colored layer 611 and a light-shieldinglayer (BM) 612 is disposed.

Furthermore, in order to seal the organic light-emitting element 517, atransparent protective layer 601 is formed. As the transparentprotective layer 601, an insulating film mainly made of silicon nitrideor silicon oxide nitride obtained by means of a sputtering method (suchas DC process or RF process) or a PCVD method, a thin film mainly madeof carbon (such as a diamond-like carbon (DLC) film, or carbon nitride:CN film), or a laminate thereof can be preferably used. When a siliconnitride film is formed with a silicon target and in an atmosphere thatcontains nitrogen and argon, a silicon nitride film high in the blockingeffect to impurities such as moisture and an alkali metal can beobtained. Alternatively, a silicon nitride target may be used.Furthermore, the transparent protective layer may be formed with adeposition device that uses remote plasma. Still furthermore, in orderto allow light going through the transparent protective layer, a filmthickness of the transparent protective layer is preferably as thin aspossible.

Here, in order to further seal the organic light-emitting element 517,by use of not only the sealing agent 505 but also a second sealing agent602, the space 507 in FIG. 5 is filled and adhered with the sealingsubstrate 504. The sealing operation may be conducted under an inert gasatmosphere. Also as to the second sealing agent 505, similarly to thesealing agent 505, an epoxy base resin can be preferably used.

Example 6

In the present example, in the light-emitting device shown in FIG. 5, alight-emitting device having a double-sided emission type structure inwhich from both of a substrate 510 side and a sealing substrate 504 sidelight is extracted will be specifically illustrated. A schematic diagram(sectional view) thereof is shown in FIG. 63. In FIG. 6B, referencenumerals of FIG. 5 will be quoted. Directions of emission are as shownwith 622 and 623 in FIG. 6B.

In FIG. 6B, a basic structure thereof is similar to that of FIG. 6A.However, it is different from FIG. 6A in that as the first electrode 513a transparent conductive film such as an ITO film or an IZO film isused. Here, by the use of an ITO film, a light-emitting device having adouble-sided emission type structure can be realized.

In FIG. 6B, on the substrate 510 side a color filter is not disposed;however, by disposing a color filter also on this side, both surfaceseach may be provided with a color filter. In this case, a color filterformed on the substrate 510 side may be disposed according to a processsimilar to that used in an existing liquid crystal display device or thelike.

Example 7

In the present example, various electric appliances that are completedby use of a light-emitting device having an organic light-emittingelement according to the invention will be explained.

As the electric appliances that are manufactured with a light-emittingdevice having an organic light-emitting element according to theinvention, a video camera, digital camera, display with goggle(head-mount display), navigation system, audio reproducing device (suchas a car audio and audio compo), note type personal computer, gamemachine, portable information terminal (such as a mobile computer,portable telephone, portable game machine or electronic book) and imagereproducing device with a recording medium (specifically a device with adisplay device that can reproduce a recording medium such as a DVD anddisplay the image) can be cited. Specific examples of these electricappliances are shown in FIGS. 7 and 8.

FIG. 7A shows a display device and the display device includes a chassis7101, a support table 7102, a display portion 7103, a speaker portion7104 and a video input terminal 7105. Alight-emitting device having anorganic light-emitting element according to the invention is used tomanufacture the display portion 7103. The display device includes allinformation display devices for use in personal computer, TV broadcastreceiver, and billboard display.

FIG. 7B shows a note type personal computer and the note type personalcomputer includes a body 7201, chassis 7202, display portion 7203, keyboard 7209, external connection port 7205 and pointing mouth 7206. Alight-emitting device having an organic light-emitting element accordingto the invention is used to manufacture the display portion 7203.

FIG. 7C shows a mobile computer and the mobile computer includes a body7301, display portion 7302, switch 7303, operation key 7309 and IR port7305. A light-emitting device having an organic light-emitting elementaccording to the invention is used to manufacture the display portion7302.

FIG. 7D shows a portable image reproducing device with a recordingmedium (specifically a DVD reproducing device) and the portable imagereproducing device includes a body 7401, chassis 7402, display portion A7903, display portion B 7404, recording medium (such as DVD) readportion 7405, operation key 7406 and speaker portion 7907. The displayportion A 7903 mainly displays image information, the display portion B7904 mainly displays textual information, and a light-emitting devicehaving an organic light-emitting element according to the invention isused to manufacture each of the display portions A and B. The imagereproducing device with a recording medium includes a home game machineand so on.

FIG. 7E shows a goggle type display (head-mount display) and the goggletype display includes a body 7501, display portion 7502 and arm portion7503. A light-emitting device having an organic light-emitting elementaccording to the invention is used to manufacture the display portion7502.

FIG. 7F shows a video camera and the video camera includes a body 7601,display portion 7602, chassis 7603, external connection port 7609,remote control receiving portion 7605, image receiver 7606, battery7607, audio input portion 7608, operation key 7609 and eye pieces 7610.A light-emitting device having an organic light-emitting elementaccording to the invention is used to manufacture the display portion7602.

FIG. 7G shows a portable telephone and the portable telephone includes abody 7701, chassis 7702, display portion 7703, audio input portion 7709,audio output portion 7705, operation key 7706, external connection port7707 and antenna 7708. A light-emitting device having an organiclight-emitting element according to the invention is used to manufacturethe display portion 7703. When the display portion 7703 displays whitecharacters against a black background, the power consumption of theportable telephone can be suppressed low.

FIG. BA shows a double-sided emission type note type personal computerand the note type personal computer includes a keyboard 801, displayportion 802 and soon. The characteristic point of the note type personalcomputer is in that as shown in FIG. 8B both emissions 803 and 804 to afront surface and to a back surface are made possible. This can beachieved by applying the light-emitting device having a double-sidedemission type structure according to the invention shown in for instanceFIG. 6B to the display portion 802. When thus configured, as shown inFIG. 8C, even in a state where the display portion 802 is closed, bymaking use of emission to a back surface, an image and so on can beobserved. A direction of opening the display portion is shown with 805.

As mentioned above, a range of applications of a light-emitting devicehaving an organic light-emitting element according to the invention isvery broad and the light-emitting device can be applied to all kinds ofelectric appliances.

1. (canceled)
 2. A light emitting device comprising: a light emittingelement comprising: a first electrode over a substrate; anelectroluminescent layer over the first electrode, theelectroluminescent layer comprising a first emission region and a secondemission region over the first emission region; a second electrode overthe electroluminescent layer; and an insulator covering an end potion ofthe first electrode, wherein the second emission region is located apartfrom the first emission region, wherein the first emission region andthe second emission region are overlapped with each other, and whereinat least one of the first emission region and the second emission regioncomprises a phosphorescent material.
 3. The light emitting deviceaccording to claim 2, wherein the phosphorescent material is an iridiumcompound.
 4. The light emitting device according to claim 2, wherein adistance between the first emission region and the second emissionregion ranges from 1 nm to 30 nm.
 5. The light emitting device accordingto claim 2, wherein the first electrode comprises a transparentconductive film.
 6. The light emitting device according to claim 2,wherein the one of the first emission region and the second emissionregion comprises a host material in which the phosphorescent material isdispersed.
 7. The light emitting device according to claim 2, whereinthe other of the first emission region and the second emission regioncomprises a fluorescent material.
 8. The light emitting device accordingto claim 7, wherein the other of the first emission region and thesecond emission region comprises a host material in which thefluorescent material is dispersed.
 9. The light emitting deviceaccording to claim 7, wherein the phosphorescent material and thefluorescent material are selected so that white emission is obtainedfrom the light emitting element.
 10. The light emitting device accordingto claim 2, further comprising a sealing substrate over the secondelectrode.
 11. An electric appliance comprising the light emittingdevice according to claim
 2. 12. A light emitting device comprising: alight emitting element comprising: a first electrode over a substrate;an insulator covering an end potion of the first electrode, anelectroluminescent layer over the first electrode and the insulator; anda second electrode over the electroluminescent layer, wherein theelectroluminescent layer comprises: a first emission region over thefirst electrode; and a second emission region over and apart from thefirst emission region, and wherein at least one of the first emissionregion and the second emission region comprises a phosphorescentmaterial.
 13. The light emitting device according to claim 12, whereinthe phosphorescent material is an iridium compound.
 14. The lightemitting device according to claim 12, wherein a distance between thefirst emission region and the second emission region ranges from 1 nm to30 nm.
 15. The light emitting device according to claim 12, wherein thefirst electrode comprises a transparent conductive film.
 16. The lightemitting device according to claim 12, wherein the one of the firstemission region and the second emission region comprises a host materialin which the phosphorescent material is dispersed.
 17. The lightemitting device according to claim 12, wherein the other of the firstemission region and the second emission region comprises a fluorescentmaterial.
 18. The light emitting device according to claim 17, whereinthe other of the first emission region and the second emission regioncomprises a host material in which the fluorescent material isdispersed.
 19. The light emitting device according to claim 17, whereinthe phosphorescent material and the fluorescent material are selected sothat white emission is obtained from the light emitting element.
 20. Thelight emitting device according to claim 12, further comprising asealing substrate over the second electrode.
 21. An electric appliancecomprising the light emitting device according to claim 12.